Noob seeking lens

[Soulreaver]

Hi all.
Thanks 4 helping a clueless noob.
I want to buy a tele zoom for that shallow depth of field and that extra range for my F80.
Nowadays I have a 28-80D.Now my options are :
1) sigma 70 300 APO Macro super.
2) sell my current lens and buy a 28-105 + a 70-300D.

That APO one has the same filter size as my 28-80, which would be a plus.The same holds true for the second pair.

What would be best?Is sigma´s APO better than nikon´s ED.
The second option would be more costly, but is it of better quality?

thanks